MHD will show the actual correction parameters. The JB4 may also be able to do it but I've never looked at them in that much detail.
The load parameter is essentially the amount of cylinder fill. The best way to think of it is that 100% load is the maximum that a non-turbo engine (some can actually operate higher but we'll keep it simple) can operate at. Anything higher than 100% is the result of forced induction, so 200% load would be twice the amount of air/fuel in the cylinder.
The relationship between boost in the manifold and load is non-linear because having twice the pressure in the manifold doesn't equate to twice as much air in the cylinder due to restrictions through the intake port. To get 200% load on the stock intake/head you make need 250% atmospheric pressure in the manifold, the ECU calculates this relationship through the "volumetric efficiency" model.
Due to software limitations in the DME, it can only see 22psi of actual boost so once you get up past 260~ load in a tune the DME will cap out on its boost target and you need to start scaling so there's no perfect solution. But you'd be a lot closer to reality reporting 250 load than 160.
I'm probably the last person you want to ask for unbiased advice on a JB4, I'd personally rather drive a stock vehicle than go anywhere near one of those. But my advice for someone that's spent a good amount of money on hardware to go single is to also invest a little in a proper tune. These days you can control a single turbo purely from the DME with no need for an external boost controller. You'd still need something to control PI but I think the Reflex is much better at than than the JB4.
Wedge does a pretty good job with tuning single turbo vehicles, he's probably the only person I could recommend on the N54 platform if you wanted to move away from the JB4.